Data storage needs continue to increase and thus the numbers and types of data storage devices are increasing correspondingly. Information technology personnel need methods to manage high-capacity data storage devices, which are sometimes configured as “libraries.” These data storage libraries often include a few tape or disk drives and multiple slots to accommodate tape or disk cartridges. A library controller communicates between the host and a robot to control the movement of cartridges between slots and drives.
In some cases, a single host computer exchanges data with a single library. However, it is more common for several computers to communicate with one or more data storage libraries, or to have a data storage library effectively partitioned for use by multiple hosts.
As a result, there is a need to manage these libraries so that each host computer or user is allocated an appropriate amount of storage capacity and drives. One client software product NETBACKUP™, provided by Veritas of Mountain View, Calif., allows multiple computers to share a library. Each user must run a client-side copy of the NETBACKUP™ software, and the software then provides library management capabilities to the users. As an alternative to a client-side software solution, an intermediate software product, such as the SCALAR DLC™ by Advanced Digital Information Corporation of Redmond, Wash., partitions a library into portions so that the library may be shared by users.
A third library management solution is described in U.S. Pat. No. 6,356,803. Under this patent, a multi-path architecture is employed in a system where drives become the interface for the host and the library. Each host is associated with one or more drives, and each drive is then associated with a partitioned set of contiguous slots. The slots are contiguously assigned, with a direct mapping between a partitioned set of slots and a given drive. Other methods of sharing or managing a data storage library may be found in the following U.S. patents/applications: U.S. Pat. Nos. 6,044,442, 6,434,090, 6,487,474, 6,328,766, and US2001/0034813.
Some of these library management solutions fool applications running on a host computer into thinking that the computer is communicating with a tape drive. Instead, however, a disk drive reads/writes data for the computer and these solutions mimic commands and signals that are typically provided by a tape drive. One product employs a fibre channel (FC) connection between a disk storage facility and an attached tape library. Disk storage is generally more expensive than tape storage, but tends to have a higher quality of service. However, for large data storage needs, a large disk storage pool can be simply too expensive for some end users, and thus they must instead employ more economical tape storage, with its lower quality of service.
In the drawings, the same reference numbers and acronyms identify elements or acts with the same or similar functionality for ease of understanding and convenience. To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the Figure number in which that element is first introduced (e.g., element 504 is first introduced and discussed with respect to FIG. 5).
The headings provided herein are for convenience only and do not necessarily affect the scope or meaning of the claimed invention.